The broad objective of the research program is to assess the role of the orbitofrontal cortex in emotional control. In recent years, the field of affective neuroscience has been advanced significantly by progress in human functional neuroimaging techniques, in behavioral analyses of neurological patients and in theoretical analyses integrating cognitive and emotional function. These advances have led to the view that the orbitofrontal cortex contributes to a variety of functions, including inhibitory control, reward-feedback expectancy, decision making under high risk, and social awareness. In the proposed research program, a four-pronged analysis will be applied. This analysis will include: 1) neuropsychological assessment of patients with frontal lobe lesions, 2) functional magnetic resonance imaging (fMRI), 3) electrophysiological recording of event-related potentials (ERPs), and 4) development of novel behavioral tests to assess cognitive function associated with emotional control. A theoretical framework, dynamic filtering theory, will be used to guide the research program. It is suggested that the prefrontal cortex acts as a filtering or gating mechanism that controls many aspects of information processing, including stimulus encoding, memory activation, response decision, and emotion. Different regions within the prefrontal cortex monitor and control different aspects of mental function. It is proposed that the orbitofrontal cortex is involved in the monitoring and control of affect and arousal. The advantage of this theoretical framework is that findings and research in the analysis of dorsolateral. prefrontal function can be applied to the analysis of orbitofrontal function. This cognitive neuroscience approach will attempt to provide an understanding of the biological underpinnings of drug abuse. In particular, issues of inhibitory control, reward-feedback analysis, and decision making will be considered in light of issues related to drug abuse, such as compulsions, cue-induced cravings, risk taking behavior.